Power transmission



POWER TRANSMISS ION Filed Feb. 12. 1940 38 INVENTOR ALFRED S.CUMMING ATTORNEY PatentedAug.18,1942 7 2,293,118

UNITED STATES PATENT OFFICE rowan 'rnawsms SION Alfred S. Cumming, Detroit, Mich., assignor to Vickers Incorporated, Detroit, Mich., a corporation of Michigan Application February 12, 1940, Serial No. 318,393

4 Claims. (01. 50-11) This invention relates to power transmissions, Referring now to the drawing, the hydraulic particularly to those of the type comprising two circuit there illustrated includes a pump in or more fluid pressure energy translating devices driven by a suitable prime mover, such as an one of which may function as a. pump and anelectric motor l2, and having a suction conduit other as a fluid motor. 5 4 for withdrawing oil from a tank [6. The

The invention is particularly concerned with delivery conduit l8 extends through a convena power transmission system of this character intional pressure responsive relief valve 20 adaptcorporating an improved reducing valve and cired to bypass oil to the tank through a conduit cuit for operating the same. In the patent to 22 whenever a predetermined pressure is ex- Harrington, 2,184,670, issued December 26, 1939, 0 ceeded in the conduit l8. there is disclosed a reducing valve having a Conduit I8 extends to the pressure port of a pressure control chamber by which the valve four-way directional control valve 24, the tank action is regulated and which permits the use port of which is connected to tank by a conof a relatively light spring for biasing the valve. cluit 26. One cylinder port of the valve 24 con- Valves of this character have gone into extennects by a conduit 28 to the inlet port 30 of a sive use and have been found admirably suitreducing valve 32. From the outlet port 34 of able for their intended purpose in a great many valve 32 a conduit 36 extends to one end of a installations. It has been found, however, that piston and cylinder fluid motor 38. From the in certain installations, where the fluid motor or other, cylinder port of the valve 24 a conduit 40 other load device which is connected to the outextends to the other end of the motor 38. A

let port of the valve is of such character that it, branch conduit 4| may lead to a second hyin itself, maintains a back pressure in the valve draulic circuit, not shown, which circuit may, outlet chamber, some diificulty is occasionally exat times, impose higher pressures in the deperienc'ed.- This difficulty consists in a delayed livery line I 8 than are desired to be imposed opening of the reducing valve when flow there- 2:, at the motor 38.

through is reversed by connecting the normal The valve 32 comprises a body 42 formed with inlet chamber of the valve to exhaust. an inlet chamber 44 communicating with the It is an object of the present invention to proport and an outlet chamber 46 communicatvide an improved control valve of the charing with the port 34. A sleeve 48 is rigidly acter described which will automatically open 30 mounted in the body 42 and is provided with freely to return flow whenever the inlet chamber a conical seat 58 at its upper end and opening is connected to exhaust. to the chamber 44. At its intermediate portion It is also an object to provide an improved a plurality of ports 52 provide communication presssure controlling valve provided, with a between the chamber 46 and the interior bore valve-operating chamber together with a pres- 54 of the sleeve 48. Above the chamber 44 the sure responsive pilot relief valve for admitting body is provided with a bore 56 coaxial with the oil to the operating chamber and a restricted bore 54. Slidably mounted in the bores 54 and passage for exhausting oil from the operating 56 is a movable valve member 58 having a conichamber whereby a constant small bleed ofi cal portion 60 adapted to close on the seat 50. flow is maintained through the operating cham- The member 58 has a reduced portion 62 below ber and the pressure therein controlled autothe portion 60 together with a piston portion 64 matically in accordance with the valve-operatslidably fitted in the bore 54 below the ports 52. ing requirements. A spring 66 normally biases the valve member 58 Further objects and advantages of the presupwardly. The lower end of the bore 54 below but invention will be apparent from the followpiston 64 is in communication With the outlet ing description, reference being had to the acchamber 46 through a bore 68 formed in the companying drawing wherein a preferred form dy and a groove 16 formed in an end cap 12 ofthe present invention is clearly shown. removably secured to the lower end of the body In the drawing: 42 by suitable fastening means, not shown.

The single figure is a diagrammatic cross sec- Removably secured t e p O e dy tion of a valve incorporating a preferred form s an e d Cap 74 av a v vep rating chamof he present invention together with a dis.- ber 16 of cylindrical form and coaxial with the grammatic representation of a typical power bore 56. The valve member 58 carries a piston transmission circuit in which the valve may be 18 rigidly secured thereto and slidably mounted incorporated. 6 in the chamber 16. The annular space beneath the piston I8 is drained by a passage 80 which communicates with a cross bore 82 and is connected to tank by a conduit 84.

For the purpose of controlling the pressure in operating chamber I6 and thereby operating the valve member 58 to regulate the pressure in chamber 48, there is provided in the body 42 a passage 86 communicating with the outlet chamber 46 and having a pressure responsive pilot relief valve 88 cooperating with a seat 90 formed at the upper end of the passage 86. The valve 88 is biased to closed position by a spring 92 the force of which may be adjusted by means of an abutment screw 94 which is threaded in a bushing 96. The latter is mounted in the end cap 14 and serves as a retainer for an oil seal 88 surrounding the body of the adjustment screw 94.

The outlet side of the relief valve 88 coinmunicates'with the operating chamber I6 through a cross passage I00. Leading from the chamber 16 is a passage I02 having a restricting pin I04 removably mounted therein to form a path of fixed hydraulic resistance. This path leads to exhaust through the passage 82 and conduit 84. There is also provided in the cap I4 a passage I06 leading from the chamber I6 to a ball check valve I08 which opens for free flow from passage I06 and which delivers such flow through a passage IIO to the inlet port 30.

In operation, with the pumpIII being driven by the motor I2 and with the valve 24 in the position illustrated, the pump delivery is directed from delivery conduit I8 to conduit 28 where it flows through valve 32 and conduit 36 to the lefthand end of motor 38. Oil returns from the righthand end of motor 38 through conduit 40, valve 24 and conduit 26 to tank. The flow entering the valve at port 30 passes to the inlet chamber 44 and through the space between seat 50 and the conical portion 60 to the interior of bore 54 where it is free to flow out of the ports 52 to the outlet chamber 46 and outlet port 34. The action of the valve is such as to regulate the maximum pressure which can be built up in the outlet chamber 46 and consequently in conduit 36 and motor 38.

As soon as the motor encounters sufiioient resistance, the pressure in chamber 46 builds up and is transmitted through passage 86 to the relief valve 88. When such pressure exceeds the adjusted pressure setting of this valve, it opens permitting flow to take place constantly into the operating chamber I6. At the same time a constant flow out of the operating chamber takes place through the passage I02, passage 82, and conduit 84 to tank.

As the pressure in chamber 46 rises, the valve 88 will open wider permitting oil to fiow therethrough at a greater rate than it flows out through the passage I04 thereby causing the piston 18 to descend against the bias of spring 66 and the pressure acting on the lower face of the piston 64. It will be seen that a, balanced condition will be reached wherein the valve 58 will move downwardly to the degree required to maintain a constant outlet pressure in chamber 46. While in such stable condition a constant fiow occurs through valve 88 and restricted passage I04, these flows being equal in quantity. The pressure in chamber I6 will be equal to the pressure on the lower face of piston 64 plus the force of spring 66 multiplied by a factor proportional to the relative diameters of pistons 64 and I8.

Should the pressure in chamber 46 tend to rise,

an increased flow would occur through valve 88 thus increasing the flow into chamber I6 and momentarily raising the pressure therein. Accordingly the piston I8 will be caused to descend, further restricting the opening at, seat 58 and causing the pressure in chamber 46 to be brought back to normal. Likewise if the pressure in chamber 46 should tend to fall, the fiow through valve 88 will decrease thus decreasing the flow into chamber 16 and permitting the opposite action to occur.

It will be seen that the valve 88 (for any given adjustment) maintains a substantially constant pressure drop between chambers 46 and |8 but permits varying quantities to flow therethrough. The flow through fixed restriction I62, however, varies inversely as the pressure drop between N chamber I6 and exhaust. Accordingly, when the pressure in chamber 46 changes slightly, say upwardly, the valve 88 changes its opening instantly, in this case opening wider, so as to maintain the fixed pressure drop between chambers 46 and 16. This immediately upsets the balance between inflow and outflow at chamber I6, the net difference between such flows being taken up by movement of piston I8, downwardly in the case assumed. The movement of piston I8 is in the proper direction to correct the initial change of pressure in chamber 46, which set this train of consequences into action, so that a stable condition is again reached.

If the valve 24 be shifted to reverse the flow in the hydraulic circuit for causing the motor 38 to move to the left, the pump delivery is directed through conduit 40 to the righthand end of motor 38 while the lefthand end thereof discharges through conduit 36, valve 32 and conduit 28 to tank. Under these conditions a free flow is insured by the action of the check valve I08. It will be seen that when the valve 24 is shifted, port 30 is immediately connected to tank. Accordingly, any pressure above atmospheric which exists in the chamber 16 may be freely exhausted through passage I06, check valve I08 and passage IIO thus permitting the spring 66 to open the valve 58. This valve opening action is expedited as may be necessary by the fact that any pressure existing in chamber 46 reacts against the lower face of piston 64. It will thus be seen that a free reverse flow through the reducing valve is produced by the action of check valve I08.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. In an adjustable fluid pressure reducing valve, a housing provided with inlet and outlet chambers, a valve between said chambers, a relatively light spring tending normally to hold said valve open, said housing having means forming a first pressure chamber tending to close the valve, means forming a second pressure chamber having a piston therein tending to open the valve, the second pressure chamber being freely connected with the outlet chamber, a. pressure responsive relief valve connected between the outlet chamber and the first chamber, and a restricted passage connecting the first pressure chamber with a tank outlet.

2. In an adjustable fluid pressure reducing valve, a housing provided with inlet and outlet chambers, a valve between said chambers, a reling and means in the chambers, a pressure atlvely light spring tending normally to hold said valve open, said housing havin means forming a first pressure chamber tending to close the valve, means forming a second pressure chamber having a piston therein tending to open the valve, the second pressure chamber being freely connected with the outlet chamber, a pressure responsive relief valve connected between the outlet chamber and the first chamber, and a restricted passage connecting the first pressure chamber with a tank outlet, the first pressure chamber having a larger effective diameter than the other.

3. A pressure regulating valve having a chamber within which the pressure is to be controlled, a main valve connecting with said chamber and having a shiftable valve member, a valve houshousing forming a pair of valve-operating chambers each with a piston therein for adjusting the position of the valve in accordance with the pressure in the operating responsive relief .valve connected between the first chamber and one of the operating chambers, a restricted passageway connecting said operating chamber with an exhaust conduit, and means for at times exhausting said operating chamber freely and independently of said restricted passage.

4. A pressure regulating valve having a chamber within which the pressure is to be controlled, a main valve connecting with said chamber and having a shiftable valve member, a valve hous I ing and means in the housing forming a pair of valve-operating chambers each with a piston therein for adjusting the position of the valve in accordance with the pressure in the operating chambers, a pressure responsive relief valve connected between the first chamber and one of the operating chambers, necting said operating chamber with an exhaust conduit, said passage normally constituting the sole control for fluid exhausting from the operating chamber, and additional means for at times controlling the exhaust from said operating chamber.

ALFRED S. Q-UMMING.

a restricted passageway con 

